X220 IPS: latency of pixels too high - slow colour switchback

Sorry guys to present you with a new problem concerning the X220 but I noticed today (only half an hour ago) that if I switch my screen to a black screensaver and wait around 15s and go back to normal screen then the colours will be "unreal" -> means they appear to bright and "undetailed" for some time (15 to 20s) and then go back to normal (it's like slowly increasing colour depth from 256k to 32bit or the latency of the all pixels is to high).

To literally talk in pictures: I have one of these standard "I-come-with-windows-please-use-me"-background pictures of a koala. In normal state I can the details of its fur. But if the I do the above the Koalas fur is more like a big grey surface.

Sadly, I couldn't capture the phenomena with a screenshot (I tried several times but no luck) so it seems to me more like a hardware issue (have an IPS panel but so far had no problem with ghosting. but I have the screen bleeding.). Also because it's late and quite dark here in Germany I can't take a good photo of it.

If a Lenovo employee should read this here are some more hints for debugging: Have a recently bought X220 (Type: 4290-W1B) and it's currently running on battery (haven't checked plugged-in yet because I'm dead tired but hopefully will have time tomorrow) with brightness level 5 (changed it to max of 15 but problem is still occuring).

Please tell me if you need more informations! And thanks for your help beforehand.